<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 层叠性：当多个选择器选中同一个元素时，会根据选择器的权重（优先级）来决定应用哪个样式 */
        .box{
            width: 200px;
            height: 200px;
            background-color: red;
        }
        .box{
            background-color: blue;
        }
    </style>
</head>
<body>
    <div class="box">
        我是div
    </div>
</body>
</html>